As for what you're saying about the physical side, I think that's much more about stamina than it is about upper body strength.
I would agree with that - also about being relaxed. I'll be 50 this year - didn't start playing djembe until I was 37, so definitely a late starter, and for may years I suffered from severe asthma and other health issues, but I'm gradually building my stamina for performing and the speed is coming bit by bit. Hey, if you look at the way some of those old masters can still play at their age, I don't see any reason why I can't still improve
This is my group, Moussou Folila - the name was given to us by Amara Kante & Amadou Kienou - meaning, 'women who play'.
[video]
http://www.youtube.com/watch?v=fIke67wN ... Rg&index=8[/video]
(I know, I have a LOT of improving to do still, and this is definitely not our best by any means - will post more video if we get it, hopefully not filmed while we're playing in full sun after a long set!)